Preparation Of Magnetic Biocompatible Nanocomposites And Their Applications In Biosensors

Recently, biosensor has become a hot research in life science and analytical chemistry areas, because of its simple operation, high selectivity and miniaturization. What's more, it has been widely used in the field of clinical diagnotic, food industry, medicine, environmental monitoring and so on. In this paper, excellent biocompatible nanocomposites are prepared by using supermagnetic Fe3O4 NPs, natural protein BSA and high surface area of Au NPs. The functionized nanocomposites are applied to construct a series of glucose sensor and immunosensors. The main research content is summarized as follows:The first part: a novel glucose biosensor is fabricated based on the preparation of Fe3O4 /bovine serum albumin/ gold nanoparticles(Fe3O4/BSA/Au) nanocomposites. The obtained magnetic nanocomposites with a BSA protein shell provide biocompatible environment for enzyme immobilization and the biomediated gold nanoparticles could promote the electron transfer. With glucose oxidase(GOx) as an enzyme model, the Fe3O4/BSA/Au NPs/GOx electrochemical biosensor has been developed. The electrochemical performance of the biosensor is investigated by cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS) and chronoamperometry. Under the optimal preparation condition, the resultant biosensor has a short response time of 0.8s, an excellent sensitivity of 115.3?A m M-1cm-2, and a linear dynamic range from 0.25 to 7.0 m M with a low detection limit of 3.54 ?M(S/N =3). The high sensitivity, good reproducibility and stability presented in this study show that Fe3O4/BSA/Au NPs nanocomposites are promising material for the construction of biosensors.The second part: Label-free amperometric immunosensors are fabricated based on the functionized Fe3O4/BSA/Au NPs/Fc nanocomposites. In this chapter, ferrocenecarbaldehyde(Fc) is used to prepare two electrochemically active compounds: Fe3O4/BSA/Au NPs/NH/Fc and Fe3O4/BSA/Au/HS/Fc nanocomposites. After the as prepared materials are conducted to GCE electrodes with the adsorption of Au NPs and anti-CEA respectively, we obtain two reagentless amperometric immunosensors for the quantification of carcinoembryonic antigen(CEA). It shows that the resulted immunosensor modified by Fe3O4/BSA/Au/HS/Fc exhibited better performance than the Fe3O4/BSA/Au NPs/NH/Fc modified electrode in terms of stability, selectivity, sensitivity and so on.The third part: Label-free amperometric immunosensor was fabricated based on the deposition of tris(2,2'-bipyridyl)cobalt(III)(Co(bpy)33+) on magnetic bio-nanocomposites Fe3O4/BSA modified glassy carbon electrode(GCE) for determination of carcinoembryonic antigen(CEA). Gold nanoparticles were subsequently assembled on the GCE/Fe3O4/BSA/Co(bpy)33+ through electrostatic interaction with Co(bpy)33+ and strong covalent bonds with BSA for immobilization of carcinoembryonic antibody(anti-CEA). The electrode fabrication process was characterized by cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS). The factors influencing the performance of the immunosensors were studied in detail. The immunosensor constructed with the high surface area of nano-Au, the positive-charged Co(bpy)33+ redox mediator and the superior biocompatible Fe3O4/BSA nanocomposites exhibited a wide linear response to CEA in the range of 0–100 ng/m L with a detection limit of 0.93ng/m L. When the immunosensor was stored at 4 ? and measured intermittently, it yielded a 4.25% R.S.D over 50 days.